1. Technical Field
The present invention relates to the field of electronic amplification of musical instruments. More particularly, the present invention relates to the use of battery driven vacuum tubes contained within or attached physically to the musical instrument; typically, but not limited to, a guitar or bass guitar.
2. Description of the Related Art
A In the paper “Tubes Versus Transistors—Is There an Audible Difference”, Russell O. Hamm makes the case for tube amplification because such an amplifier can be operated in the overload region without adding objectionable distortion. Vacuum tube amplifiers are regarded highly by musicians, for the characteristic tone they produce.
The power supplies in these amplifiers are generally dangerous because of the high operating potentials. The components are often large, heavy, and expensive. They also require a separate lower voltage filament heater. A musician may utilize a stand-alone tube preamplifier coupled with either a tube, solid-state or hybrid power amplifier (part tube and part solid-state), utilizing the preamplifier to ‘color’ the sound. The preamplifier does not have to support the high volume levels of the power amplifier and can give a musician acceptable tone over for use with a range of power amplifiers.
Preamplifiers may be built into the instrument (i.e. on-board preamp), and are typically used in electric or so-called electric-acoustic guitars and basses; but are composed of solid-state semiconductors, and utilize amplifying devices such as transistors and operational amplifiers (i.e. op-amps).
It would be an improvement in the prior art to develop a battery powered tube preamplifier contained within the instrument (i.e. on-board preamp). In this case the battery must supply both the heater filament and safe tube operating voltage for a length of time of at least a typical performance. The few cases of prior art that attempt to utilize low voltage tube circuitry present these units as a stand alone preamplifier or amplifier, supplied from a conventional AC supply.